October 14, 1897] 



NATURE 



573 



other according to their crystal volume or their actual volume 

 as the case may be. (6) Many crystals which have heretofore 

 been considered eutropic or isomorphic are not so, since they 

 probably possess a larger or smaller molecular weight according 

 to the number of atoms. 



The additions to the Zoological Society's Gardens during the 

 past week include a Common Marmoset (ffapale jacchus) from 

 South-east Brazil, presented by Mrs. A. H. Browne ; a 

 Crowned Duiker-Bok {Cephalophus coronatus, i ) from West 

 Africa, presented by Mr. A. Nightingale ; a Nightjar (Capri- 

 initials eiiropaus), British, presented by Mr. Richard Catter ; 

 a Dusky Parrot {Piomis ftiscus) itom Guiana, presented by Mr. 

 F. Scammell ; a Scarlet Snake ' {Cemophora coicinea), an 

 American Black Snake [Zamenis constrictor), two Testaceous 

 Snakes {Zamenis flagelliforniis), a Mexican Snake {Coluber 

 melanoleiicus), a Hog-nosed Snake {Heterodon platyrhinos), a 

 King Snake {Coronella gettila) from Florida, presented by Mr. 

 J. H. Fleming ; a Soemmerring's Gazelle {Gazella soemmer- 

 ringi, 6), & Striped Hyaena {Hycena striata) from Egypt, 

 deposited; a Golden Plover {Charadrins plnvialis), a Grey 

 Plover {Squatarola helvetica), a Ringed Plover {^'Egialitis hia- 

 iicula), a Bar-tailed Godwit {Limosa lapponica), British, an 

 Eyra {Feiis eyra) from South America, purchased. 



OUR ASTRONOMICAL COLUMN. 

 Conjunction of Venus and Jupiter,— These brilliant 

 planets may now be observed near together in the morning sky, 

 and are rapidly approaching each other. Conjunction will 

 occur on October 19 at gh., when Venus will be only 0° 28' N. 

 of Jupiter, but they will be below our horizon. As a spectacle 

 for the naked eye the varying positions of the two objects will 

 be very interesting at about this period. Their times of rising 

 and distances from each other on several mornings will be as 

 follows : — 



The star t; Virginis (mag. 4-1) will be about 5° E. of the 

 two planets on October 20. Venus will pass 0° 15' N. of the 

 star on October 23, while Jupiter will pass 0° 15' S. of it on 

 November 15. On the mornmg of October 24 the waning 

 crescent of the moon will be about f S. of Venus, and a similar 

 distance S.E. of Jupiter. 



Conjunctions of Venus and Jupiter are not separated by 

 a constant interval, but occur once at an interval of about 

 304 days, and then twice at intervals of about 443 days, 

 as the following table of twelve conjunctions ending with 

 that of October 29, 1899, will show. But this sequence is not 

 invariable, for in the years 1861, 1862, and 1863 and 1882, 1883, 

 and 1884, three successive conjunctions occurred at the interval 

 of about 443 days. 



Date of P „ „ Relative Interval 



conjunction. vr.n.x. positions. in days, 



h. ^ , 



1888 January 2 ... 4 ... 9 i 51 N. ... — 



1888 November i ... 9 ... i 31 S. ... 304 



1890 January 18 ... 21 ... o 26 S. ... 443 



1891 April 7 ... 9 ... o 13 N. ... 444 



1892 February 5 ... 22 ... o x S. ... 304 



1893 April 28 ... 17 ... o 4N. ... 448 



1894 July 19 ... 20 ... o 51 S. ... 448 



1895 May 18 ... 4 ... 25 N. ... 303 



1896 August 2 ... II ... o 40 N. ... 442 



1897 October 19 ... 9 ... o 28 N. ... 443 



1898 August 19 ... 6 ... I 51 S. ... 304 



1899 October 29 ... 13 ... 9 o 33 S. ... 436 



NO. 1459. VOL 56] 



On October 21 next, at about 6 45 a.m. the relic of the great 

 red spot, if still visible, will be presented nearly on the central 

 meridian of Jupiter, and if the weather is clear, an excellent 

 opportunity will thus be offered for securing an early observa- 

 tion of this remarkable feature 



The Level of Sunspots.— Prof. H. Ricco brings together 

 some statistics in reply to the recent discussions relating 

 to the question of "Are sunspots cavities or not?" {Astro- 

 physical Journal for August). The observations discussed were 

 derived from a series of drawings of sunspots made by the 

 method of projection in the years 1880 to 1890 at Palermo with 

 a refractor of 0'25m. aperture, and at Catania with a refractor 

 of 0"33m. aperture. The projected image was in all cases 

 o'57m., a size sufficient to satisfactorily show the principal 

 details of the spots. The result of the discussion, as will 

 be seen from the following figures, shows that the number of 

 spots near the limb, whose projected form gave a result 

 conforming to the theory of Wilson, greatly exceeds the number 

 of contrary or uncertain cases. The facts show, that from 

 the years 1 881 to 1892 the proportion of cases favourable, un- 

 favourable, and neutral, were in the proportion of 7*3 to i to 2. 

 If greater weight be given, as Prof. Ricco says, to spots near the 

 sun's limb, the penumbra of which conforming to the appear- 

 ance of a cavity seen in perspective is invisible on the side 

 opposite the limb, " I have found twenty-three cases of tliis 

 sort in the eleven years, and only one contradictory case." Prof 

 Ricco acknowledges the importance of the problem of the 

 constitution of sunspots and the difficulties involved, and advo- 

 cates Mr. Evershed's suggestion that the radiations of sunspots 

 should be studied in a more complete manner. 



The Orbit of Comet 1822 IV.— On July 13, 1822, Pons, at 

 Marlia, near Lucca, in Italy, discovered a comet which, two 

 months later, reached its maximum brightness, developing about 

 this time a stellar nucleus of the ninth or tenth magnitude. The 

 observations extended over a period of several weeks, and the 

 most satisfactory elements computed were obtained from the 

 investigation carried out by Encke. A new and interesting 

 computation of the elements of this comet has been undertaken 

 by Dr. A. Stichtenoth ( Unterstuhung iiber die Bahn des Cometen 

 1822 IV., Leipzig, 1897, W. Engelmann) in his Doctor's disserta- 

 tion presented before the Gottingen faculty. Thesenew elements, 

 which are not found to differ very much from those obtained 

 by Encke, depend on 456 observations, which for the most part 

 have been reduced directly from the original observations. 

 Referred to the ecliptic they are as follows : — 



T = 1822 October 23772734, Paris M.T. 

 Log q = 0*0588426 



a =92 44 23-01 1 



/ = 127 20 47'95 ( 1822-0. 



« = 181 4 38 08 \ 



e = 09963021 



The investigation tells us that the period of revolution corre- 

 sponding to the above value of the eccentricity, namely 

 0-9963021, amounts to 5449-0 years; but on account of the 

 length of the elliptical orbit, this value of the eccentricity can 

 be varied considerably without in any way interfering with the 

 calculated positions : thus the period of revolution may be said 

 to lie between 4504 and 8748 years. 



A point of additional importance and of considerable interest 

 which this new discussion of the observations discloses, is that 

 an examination of the original manuscripts of Gambart and 

 Olbers shows that the appearance of this comet was somewhat 

 analogous to that of Comet Holmes. Gambart observed, 

 namely on 1822 July 26, a sudden brightening of a stellar-like 

 condensation in the nucleus, which at the beginning of August 

 had completely disappeared. On September 20 and 21 Olbers 

 observed a similar increase in brightness, but the decrease took 

 place more slowly than in the previous case. It appears, there- 

 fore, that sudden variations in the brightness of the cometary 

 matter which occurred in this comet were similar to those 

 which were recently noticed (1893 January 16) in Comet 

 Holmes, and can be easily explained on the meteoritic 

 hypothesis. 



The above interesting fact, cotuiected with this nearly for- 

 gotten comet, adds an extra feature to this most thorough and 

 complete " Arbeit," and Dr. Stichtenoth is to be congratulated 

 on bringing his computation to such a successful issue. 



